Abstract
ABSTRACT This work evaluated the effect of soil water availability on growth and productivity variables of cowpea in northeastern Pará, Brazil. The experiment was carried out in a field of 2,100 m2 at the experimental site of the Federal Rural University of Amazon, during the driest season of the years 2011, 2012 and 2013, in a completely randomised design with two treatments (irrigated and non-irrigated), both with 12 replications in the reproductive phase (2012 and 2013). Growth and productivity data were submitted to analysis of variance with two variation factors (water regime and experimental year) at 5% probability. Student's t -test at 5% probability was used in the means of the stomatal conductance data, since this was monitored only in 2012. Final biomass production presented a reduction of 54.3% in 2012 and 26.4% in 2013 as a result of water deficit (DEF) of 76 and 26 mm, respectively. Mean stomatal conductance was reduced by 73% in the grain-filling stage as a result of the lower water availability during this period. Average cowpea productivity under water deficit reached 1,257 kg ha-1 in 2012 and 1,396 kg ha-1 in 2013. The reduction in water supply over the reproductive period significantly decreased production by 72 and 41% (F test, p < 0.05) in 2012 and 2013, respectively. An accumulated water deficit during the reproductive phase caused a maximum LAI reduction of 47% in 2012 (DEF of 76 mm) and of 13% in 2013 (DEF of 26 mm).
Highlights
Water availability is one of the most important environmental factors in plant growth control (NASCIMENTO; PEDROSA; SOBRINHO, 2004), and the Amazon region presents a high volume of rainfall compared to other regions of Brazil, the climatic regime of this area limits cowpea production to the first half of the year, when water is readily available without the need for alternative supply through irrigation
Results of Paiva et al (2005), obtained for the common bean, show that reduced water supply caused a decrease in stomatal conductance in the reproductive phase
The cultivar BR3 Tracuateua showed significant productivity reduction as a response to water deficit in the reproductive phase, between 26 and 76 mm imposed in the non-irrigated treatment
Summary
Water availability is one of the most important environmental factors in plant growth control (NASCIMENTO; PEDROSA; SOBRINHO, 2004), and the Amazon region presents a high volume of rainfall compared to other regions of Brazil, the climatic regime of this area limits cowpea production to the first half of the year, when water is readily available without the need for alternative supply through irrigation. Silva and Neves (2011) cultivated 20 cowpea genotypes in the Northeast of Brazil, with productivities ranging between 669 and 1,070 kg ha-1 under dry conditions and between 982 and 1,832 kg ha-1 under irritation. This represents an average increase of 69% in productivity as a result of water supply. Cowpea has a large relevance in the State of Pará, its production and productivity has been decreasing since 2003 due to several technical, commercial, political and, above all, climatic problems (REBELLO; COSTA; FIGUEIRÓ, 2011)
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